The present invention relates generally to an improved clutch of the type known as a torque limiter, mechanical fuse, or torque overload release clutch. Generally such clutches perform safety and protection functions in that they prevent transmission of torque from a first device to a second device when the torque is above a set magnitude called the "trip" torque, while drivingly interconnecting said devices below said trip torque. The inventor has discovered that the trip torque at which the clutch disengages the devices, for most prior art clutches of this type, is a variable dependent jointly on the level of torque applied and the number of rotations at said level. This dependence can be called Kinematic sensitivity. He has further discovered that reducing frictional losses within the clutch can reduce the effects of this dependence.
An object of the present invention is to provide a torque overload release clutch which has a manually selectable level of trip torque and which exhibits lesser Kinematic sensitivity.
A further object is to provide such a clutch which can react to an applied overload torque in either direction, as well as accommodate rotation in either direction.
A still further object of the present invention is to provide such a clutch which requires reduced force during its manual reset or which is alternatively capable of being automatically reset.
These and other objects of the present invention are met in a torque overload release clutch comprising a first assembly, an intermediate assembly, a second assembly, first interconnecting means for drivingly interconnecting the first assembly and the intermediate assembly, said first means including a plurality of balls disposed therebetween, second interconnecting means for drivingly interconnecting the intermediate assembly with the second assembly comprising a plurality of balls disposed therebetween, means for generating a reference force and applying said reference force to said second interconnecting means, wherein the first, intermediate and second assemblies and the first and second means together operatively form a drive train for transmitting torque between the first and second assemblies when the intermediate assembly is in its engaged position, and wherein the intermediate assembly is adapted to move axially to a disengaged position thereby disabling the second means when the axial force due to the torque applied to the second means exceeds the reference force applied thereto and thereby interrupting the transmission of torque between the first and second assemblies.
According to a further aspect of the invention, the torque overload release clutch further includes latch means for maintaining the intermediate member in its disengaged position. According to a preferred embodiment, the latch means includes a dilating ring of latch balls which (i) interconnect the force generating means and the intermediate assembly, thereby transmitting the reference force therebetween when the intermediate assembly is in its engaged position, and (ii) interconnect the force generating means and the first assembly thereby transmitting the reference force therebetween when the intermediate assembly is in its disengaged position.
According to yet a further aspect of the invention, the ring of latch balls can assume an intermediate position in which the reference force is transmitted in parallel to both the first assembly and the intermediate assembly so as to facilitate resetting of the clutch after disengagement.
The above and other aspects of the invention, including various novel details of construction and combination of parts will now be more particularly described with reference to the accompanying drawings. It will be understood that the particular device embodying the invention is shown by way of illustration only and not as a limitation on the scope of the invention. The principles and aspects of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.